This is not how I would log inventory changes, but I see no iOS specific issues with your script.
Try this "cheap fix" and see if it helps:
Double click your home button.
Find the icon for FileMaker GO and "flick" it up to close the application.
Re-open FileMaker Go. Open your file and test this script again to see if it still fails.
That did not help. I was playing around with the Manage security "accounts." I have to limit most things for a particular group of people who will be using the feature of taking units out. Did I maybe restrict too much and make it so they can't make changes on other layouts?
Also how would you suggest logging inventory changes?
You may have the "available menu commands" set to restrictively for this to work--that's a commonly encountered issue.
For how I recommend logging inventory: Managing Inventory using a Transactions Ledger
If you aren't testing the script with a full access privilege set when you have it open on the iPad, try selecting the "run with full access privileges" option in the script editor.
Another debugging trick is to temporarily add some Show custom dialog steps that pause the script to display data from key fields. You can then run the script and check the values popping up in the custom values dialogs to try to isolate which part of the script is failing to work.
Also, are you using a custom menu here? If so, temporarily set it back to a standard menu set and see if that makes any difference.
Selecting the run with full access privileges button worked! Which makes sense because I probably restricted the set the privilege set too much to the point where it didn't work on the iPad under the given account! Thank you very much :)